Education and Meanings

Antioxidants: Understand what they are and what they are for05

Antioxidant molecules are agents responsible for inhibiting and reducing damage caused by free radicals and preventing cell oxidation, since they can impair the normal functioning of cells and cause mutagenic and degenerative effects, accelerating aging.

Thus, the role of antioxidants is essential for protecting healthy cells and for controlling the harmful actions of free radicals in our system.


Free radicals are generated and released every day into the bloodstream through various metabolic reactions. They are molecules with one electron less, a fact that makes them highly unstable and reactive.

In the search for balance, these molecules try to “steal” electrons to complement their structure by joining with other molecules, such as proteins, lipids and DNA. At this junction, they can disrupt the normal performance of cells, resulting in problems such as cell oxidation.

When under normal conditions, free radicals are self-neutralizing and their effects on humans are favorable, however, if the level of these substances increases, there is a junction of impurities that can lead to degenerative processes such as cancer and aging.

Therefore, antioxidant self-defense has the function of stabilizing the action of free radicals, preventing the production of excess toxicities and, consequently, cell destruction. To neutralize the action of free radicals, antioxidants need to join with them, stabilizing the molecule by sharing electrons, and ultimately preventing the oxidizing action in our body’s cells.


Studies indicate that a diet rich in the consumption of antioxidants considerably reduces the risks of major human diseases, such as cancer, diabetes, cataracts, arthritis, premature aging, cardiovascular diseases, Alzheimer’s and Parkinson’s, as it helps to reduce the situation of imbalance between levels of antioxidants and free radicals.

Thus, when we talk about the importance of antioxidants, we emphasize the fact that they are essential to controlling the amount of free radicals in the body, preventing the harmful damage they can cause.


The antioxidant defense system is responsible for capturing and eliminating excess free radicals from our bodies. These antioxidants are made up of enzymes, vitamins and minerals, however, not all of these components can be produced by the body, making it necessary to ingest these substances through food.

With that, we can say that there are two types of antioxidants, which are called enzymatic (naturally produced by the body) and non-enzymatic (acquired through food).


The enzymatic system is formed by substances produced naturally by our body. This system is the first to act to prevent the accumulation of free radicals such as Hydrogen Peroxide, Superoxide, Single Oxygen, Hydroxyl Ion, Nitric Oxide and Nitrous Oxide. Endogenous antioxidants are formed by several enzymes, including:

  • Superoxide dismutase (SOD): enzyme that catalyzes the dismutation of the radical anion, transforming two superoxide radicals into a hydrogen peroxide; 
  • Catalase (CAT): acts on hydrogen peroxide, transforming it into water and oxygen;
  • Glutation peroxidase (GPx): enzyme that reduces hydrogen peroxide and organic hydropeptides using glutathione (GSH) and acts as a co-substrate of GPx, with the property of an electron donor, which can be regenerated through glutathione reductase (GR) with hydrogen transfer from NADPH.

Over the years, the enzymatic defense system loses its efficiency, as it tends to weaken during the natural aging process.


Exogenous antioxidants are composed of groups of substances, such as vitamins, plant substances and mineral salts, which need to be absorbed through proper nutrition.

The main non-enzymatic antioxidants are:

Vitamin C: Vitamin C, or ascorbic acid, is normally consumed in high doses by humans because it is one of the most important antioxidants. It is easily found in citrus fruits like oranges , lemons and acerola , as well as vegetables like broccoli , peppers and tomatoes . Its action regenerates alpha-tocopheryl into alpha-tocopherol and inactivates the hydroxyl free radical, making it crucial to contain the beginning of propagation of lipid peroxidation. Vitamin C plays an important role in protecting the skin from damage caused by exposure to solar radiation.

Vitamin E: Vitamin E is a component of naturally occurring vegetable oils that are rich in polyunsaturated fatty acids, however, it is also present in oilseeds and whole grains. In the body, it is a substance that has a protective factor for cell membranes, blocking the initiation and propagation of lipid peroxidation. Its action can prevent free radical damage associated with diseases such as arthritis or cataracts.

Beta- carotene : Beta-carotene or carotenoids are natural colorings present in yellowish or orange-colored foods, such as carrots , tomatoes , oranges , peaches , pumpkins , and also in dark vegetables. This water-soluble vitamin is excellent for looking for free radicals in a low oxygen concentration and acting as an antioxidant, protecting cells from the harmful effects of free radicals.

Vitamin A: Vitamin A is an important factor in cell growth and differentiation, as it has the ability to combine with free radicals before they damage them. Its action presents preventive factors in the development of bladder, breast, stomach and skin tumors. This vitamin compound can be found in foods such as carrots , spinach , mangoes and papaya .

Flavonoids: Flavonoid antioxidant compounds are a set of natural substances that have diversified biological activities such as anti-platelet aggregation, anti-inflammatory and antioxidant, therefore, responsible for eliminating free radicals from our body through the inhibition of the enzymes that produce them. These substances are able to prevent cardiovascular disease and can be found in red colored fruits such as grapes , strawberries and apples , and also in vegetables such as broccoli , spinach , parsley and kale .

Curcumin: Curcumin is a phenolic compound used as a food coloring and flavoring, it acts as a natural antioxidant originating from the roots of turmeric. This substance scavenges free radicals, inhibiting lipid peroxidation, acting in the cellular protection of cellular macromolecules, including DNA, from oxidative damage. It can be found in foods like turmeric and curry, for example.

Selenium: This mineral substance forms the active center of several antioxidant enzymes, including glutathione peroxidase. It works together with vitamin E, in addition to having a high antioxidant power. Its action helps to prevent certain types of tumors and to strengthen the immune system. Selenium can be found in plant foods such as corn , wheat and rice and in animal products such as meat, fish, chicken and eggs.

Copper and Zinc: These are substances similar to selenium, that are, they act as microelements that form an essential part of the various antioxidant enzymes. These two mineral substances are responsible for influencing the action of the superoxide dismutase enzyme, being fundamental in the enzymatic system. Copper can be consumed through foods such as chickpeas , lentils , sunflower seeds , peanuts , beans , among others. Zinc, on the other hand, can be found in pumpkin seeds , cooked soybeans , almonds and peanuts .


The action of antioxidants is associated with fighting many diseases, which is why maintaining a balanced diet is important to ensure the functioning of various activities in our body. The consumption of foods rich in antioxidants is one of the defense mechanisms against free radicals and helps to promote cell protection.

We have already seen that there are a number of foods rich in antioxidant substances, but it is worth reinforcing some of them, such as citrus fruits, dark green vegetables, wheat germ, soybean oil , rice , carrots , pumpkin , melon , meat, milk, among others.


Under normal circumstances, our internal defense system is sufficient to protect us. Since people have different vitamin needs, in some specific cases, it is necessary to supplement some antioxidant enzymes.

However, it is always recommended to prioritize the intake of antioxidants through a proper diet, leaving the use of vitamin supplements to the last case and only under medical recommendations.

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Robert Asprin, APD is a non-dieting Accredited Practicing Dietitian passionate about inspiring positive changes in eating and lifestyle behaviors to help improve health while nurturing relationships with food and body.

Robert Asprin

Robert Asprin, APD is a non-dieting Accredited Practicing Dietitian passionate about inspiring positive changes in eating and lifestyle behaviors to help improve health while nurturing relationships with food and body.

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